Can't switch to weapon's menu, help me?

Answers

Do you mean the one whe you press the R1 button. There are times that you can open this menu and these are:

1. Status AilmentsA. If you're inflicted by the status "Seal". You cant' use any skill your on this condition.B. If you're "Paralyzed". You can't use any skill and you can't move your character in this condition.C. If you're inflicted by "Charm" . You can't use any skill and you attack your own allies when in this condition.and,D. IF you're "Confused". This also like the skill Charm but there are chances that you're character will attack the enemies.

2. Wait for the bar line to be full. ( The one that is shown when you activate a skill, it is located on the top of your player's head ) You must wait for this bar to full to activate the menu and execute another skill.

I hope this may help you. If there's any problem with my post, just ask another question. :)